So does the non HG+ cassettes of 12 speed Shimano 105 work on the H3?
Hg cassette should fit on the new hubs. Theyāre supposed to be backwards compatible.
Iām unable to in all any 12spd Shimano cassettes on the H1/H2/H3 units I have due to the sloppy manufacturing tolerances of the hub bodies those trainers have. They absolutely should install fine as HG+ splines are backwards compatible with HG hubs. Sarisā hubs were slightly out of spec.
Iād assume theyāve made a running change to resolve this on existing stock.
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I guess when the time comes Iāll have to see if the 12 speed fits on mine and the specs arenāt as off as yours. Hate having to buy another compatible unit for this.
And now it seems that REI is on the ropes?! It seems their new CEO did the same thing that killed Bed Bath and Beyond: Try too hard to compete with the low end retailers?
BB&B brought in the same cheap garbage other stores, and online were hawking, and started announcing endless sales and other promotions, and in the past month or so Iāve gotten several (hundreds?) or sales and promotions from REI.
What is it with the CEOās that get into power and run the corporations into the ground, and move on to do it yet again. I guess as long as shareholders benefit, itās all good?
Iāve been a āmemberā of REI for DECADES, and will be pissed if they go belly up, especially for such a stupid reason. The last time I was at their local store (2 hours away) it was hard to find someone to help with questions. Iāve got a huge dividend coming next year too. Itās worked out that I buy the big stuff from them, but also commodity items too at timesā¦
Do they have classes in how to kill corporations at those MBA schools? And why does it take so long to get rancid leadership out? (Although I read that one noxious CEO was canned, and still ended up with a 6-figure āparachuteā and 18 months salary, JUST FOR BEING REMOVED!! They won, and the corporation still has to pay to get rid of them? Astonishingā¦ Failing up?
And, locally, restaurant after restaurant is closing. The race to the bottom is accelerating.
I have a friend whoās worked at REI for a number of years. They said that the supply chain issues caused by the pandemic were a shock and the company chose to pick up more, often cheaper products, to make sure they had inventory of something. I suspect we are still feeling the hangover from this.
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I get it, but the stuff at BB&B was just junk. Like embarrassing junk. People were also returning things, and then buying the returns at a lower price too. 
Is it possible to just use a 12 speed system with an 11 speed cassette on the H3 instead if I canāt get a Shimano 12 speed cassette installed? I just use ERG mode anyways.
Ive done all 3 variations you can do with a 12 speed bike on a Saris H3.
First just ran the 12 speed bike on the current 11 speed cassette (with 12 speed chain) on erg mode and that works well. But I also wanted to do more than just erg mode.
I then bought a shimano hub compatible 12 speed cassette (ZTTO) on Alixpress and tried that. Flawless on erg and a solid 8/10 for shifting in Zwift. Does it work, yes, is t perfect, no? All depends on how picky you are.
I then went to the final step and purchased the XDR hub adapter and installed a 12 speed sram force cassette. Iād give this a 9/10 since it works perfect except for the fact that I canāt get in the 33 cog because itās too close to the trainer. Everything else is flawless.
I still have a hard time understanding why a 12 speed ZTTO cassette fits the hub but shimano 105 12 speed wouldnāt. Iām guessing with the ZTTO you canāt use the biggest cog also? So out of the three setups, which would you recommend if youāre just using the trainer in ERG mode? Coming from 10 speed ultegra, so will have to buy new cassette regardless of setup.
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I think Iād recommend the ZTTO setup if you have to buy a new cassette regardless. It gets you 90% of the way there, is affordable, and allows a bit of flexibility if ever you step away from erg.
Just getting back into riding lately, picked up an H3 on sale. First ride, I felt like I had to put more effort in, so I dual recorded the H3 with my Stages L crank power meter on a quick test ride. It seems to be showing around 10-12% lower than the Stages. I read a bunch of posts on this thread about perhaps the top hat spacer causing more friction, so Iām planning to check that shortly, as well as the unit itself needing a few weeks for the bearings to loosen up. Any other ideas or could my Stages just be reading higher in error?
You really canāt compare a left-only crank power meter with a a device that measures total power.
Either use Power Match to keep your current settings / feel or adapt to the new settings on your H3. The reality is that the H3 is going to be more accurate and a better representation of your true FTP
Sorry. 
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Have you calibrated the PM and trainer?
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THAT!!! And a top hat isnāt going to increase resistance because it doesnāt turn (did you use the adapters included with the H3?), isnāt meant to turn. (I mean, if we are talking the same thing)
Calibrating is the key to having more accuracy. I never (well, skipped it once or twice with erratic results) took off on a ride without calibrating first. DO IT religiouslyā¦
Iāve calibrated both multiple times. Iām just going to power match to my crank to have similar metrics when riding indoors vs outdoors and call it a day. Thanks guys!
Have you tried fresh (new store bought) batteries in the Stages? I swear the Stages would get wonky with older batteries.
I know it doesnāt help, but my H3 was off by quite a bit less than yours. Well so that means that either the H3 was accurate, so to speak, or the other side of the equation was off too but in the same ādirectionā as the H3.
I spent an afternoon chasing āaccuracyā in tire pressure gauges and it was an experience. I cam to the conclusion that all of them were off, and the sample size was 6. It was on a lawn tractor tire that required 12PSI, and obviously a huge error would be a problem, and the errors ran over 20%, in a hookless bead tire (they all seem to have gone tubeless for some insane reason)
Something is wrong somewhere. Can you borrow someones power pedals to test the system?
I use the same. Set up. Use the crank for cadence and trainer for power. Thereās also going to be loss from the driveline but not as much as what youāre seeing.
The batteries are green but putting a new set in definitely wouldnāt hurt. Iāll give that a shot when I can. I might be able to find some pedals to borrow, that would definitely be the best way to test all three together.
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I have a set of Assioma pedals and they are usually right on and for the cost, one of the best things Iāve ever bought. They really work quite well. I ended up with Rallyās (SPD-SL) but Favero has a way to do Shimano cleats now. Just a suggestion, since Stages seems ālights outā possibly forever.